Steam-superheater for boilers.



'I'. M. RENDGHEN. STEAM SUPBRHBATER FOB. BOILERS.

APPLICATION FILED JAN.3O,A1912.

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THEODOR MARTIN RiENDCI-IEN, 03F ALTONA-OTTENSEN, GERMANY,VASSIGNOR, BY

MESNE ASSIGNMENTS, TO LOCOMOATIVE SUPERHEATER COMPANY, OF WILMING- TON, DELAWARE, A CORPORATION F DELAWARE.

if jS'rEAM-SUPERHEATER ron. Bomans.

Specification of Letters atent. Patented Jul'y 1, 1913,

Original application filed March 11, 1908-, Serial No. 420,472. Divided aiidiths application ied January 3o, 1912.' seriai No. 674,331.

To all whom t may concern: ,I l Be it known that I, THEoDoR. MARTIN f RENDGHEN, a Subject of the German'Emperor, and resident of Altona-Ottensen, the. German Empire, have invented certain new and useful Improvements in Steam- -Superlieaters for Boilers, of whichthe following is a specification. f

This application is March 1l, 11908.

My invention relates especially to steam i superheaters of the smokeftube type, z'. e.,

superheaters in which the steam to be superheated is passed through superheater tubes which are arranged in a plurality of the smoke or fire tubes of the boileigithe superheater tube in agiven smoke tube returning upon itself and being provided with a return bend for the purpose of suchreturn which bend usually lies wholly within the smoke tube between `the two tube sheets of' the' boiler. rv More especially my invention relates*` to the construction and character of this re turn bend by virtue of which I obtain certain marked advantages asv will hereinafter appear. he object of my invention is to produce a superheaterof the type specified having superheater tubes provided with return bends which by their form and construction permit said superheater tubes to have a maximum cross. sectional area without restricting saidarea at the bend, and with a minimum restriction of the cross sectional area of the smoke tubes in which saidsuper'f,

. Fig. 2 is a longitudinal section, and Fig. 3

a division of my 'earlier application, Serial No. 420,472, filed a .superheater tube arranged in accordance with and embodying my invention, and Figs. 5 'a'.'d 6 are separate detailed views illustrating the preferred mode of construca cross section of a boiler smoke tube'.(unessential `parts being broken away)`-,i cnii ta in ing 'a superheatcr tube of another Well-krioiig'n-Q- 4 construction; Fig. 4- is a longitudinals'etir tsimilar'ly vbroken away) through a plurality of boiler smoke tubes containing each` -Steam. superheaters, of the general type herein referred to,ai e'known in which the superheater tubes connected with collectors suitablyarranged in theboiler 4pass through the boiler smoke tubes in such a manner that each ofthe superheater tubes proceeding from one of the collectors is carried toand fro in each oione or more of. said .smoke tubes and is then connected with the .other collector, the return bend of the supertieter'tu-be being located inside the boiler `One of the most usual and obvious forms of pairedsuperheatertubes, or superheatei element with return bend, is that illustrated in Fig.fl in which a single length oftu-be is bent back upon itself to provide the tivo .legs b b united by the return bend a. This bending even if done with the utmost care and in the mostr approved manner as c. g., by suitably heating the tube where it A is to be bent, and by packing the tube, at andv near the part to be bent, with 'sand or consequent diminution of cross section.

When it is attempted tobend the tube so" other .suitable medium, invariably results in l a flattening of the tube at the .bend andin a in order not to require that a smoke tube of unduly great diameter be used, the relative flattening `of the tube at the bend and Consequent relativo diminution of cross section at thatpointbecomes much greater. Inbends madeas ,above set forth the smallest permissible mean radius of bending which maybe employed for superheater tubes to be used `in superheaters Aof the type referred' to without excessive restriction of cross .section at the bend and consequent. inethciency of operation 1s the. outer diameter of the tube to be bent z'. e., the legsofA4 the tube of the bending may not be separated by a dis-` will be less if a smaller diametered superheater tube be employed but this, of course, results in a less volume of steam passing through said tube, as well as in a greater loss of steam pressure, from one collector to the other. Q i

In order to completely avoid any reduction in the cro'ss section'of the superheater tube, at the return bend the construction illustrated in liigs. 2 and?) is sometimes employed. Here the return bend consists of a special piece a2, usually a casting and known as ia return bend, into which thetwo lengths, or legs, of tube b2 are tted. This bend a2 must be .made with walls of suicient strength to withstand the, generally very high, pressure oflthe steam from which it results that the free cross section .of the.

boiler tube is reduced especially by the enlarged socketl portion a3 of the ben'd into f which the superheater tubes are fitted thereby impeding the free passage of the heating gases in a highly prejudicial manner. In` this case also it is only possible to partially obviate this defect bythe employment of superheater tubes having a pr'ejudicially small relative diameter.

AThe `connection of the two lengths of superhe'ater tube arranged inside the boiler tubejnaccordance with either of the construetions just described, that is to say, bv

the return bend formed inthe tube itself by bending a single length back upon itself or by a special separate bend presents grave disadvantages the chief of which is that in the rst' case fthe relative cross section of the superheatgube lis reduced so that thev steam is tbittled, while in the latter case the relative oss section of the smoke tube `is reduedr'f-bereby there results a smaller flow of the'fire gasesvand hence a restriction of the heating power.

My presentinvention has for its object to avoid the difliculties and disadvantages above referred to and .utilizes a superheater tube preterably formed by bending a tube length back upon itself so as to permit the two legs to be brought very close together without flattening t-he tube at the return bend and without in any way restricting the Vvcross sectional areal at such bend; this preferred way of bending the tube also enables a. return bend to be provided which will lie substantially entirely between they opposite outer portions of the peripl'ieries of the two legs, z'. c., which will neither bend nor be ex.

panded outwardly beyond either leg in the plane of the two legs or laterally7 as to said plane. The superheater tubes thus formed, in combination with the smoke tubes in which they are inserted, comprise my in# vention, and provide an arrangement in which superheater tubes may be used vwhich lare of larger diameter than hitherto relative to said smoke tubes for an equal obstruction of lire gases, or else in which superheater tubes, of the same-diameter as hitherto rela-f `by bending the tube in such a manner that all pressing or upsetting of the material I which might flatten the tube is avoided. lVith this object notches or recesses c (Figs. 4 6) are formed on the inner sides of the superheater tubes b at the' places where the ybends a are to be formed. The notches c are so formed 4and arranged "that their edges meet after the two legs b have been bent parallel toone another, that is to say, when the curve or return bend has been completely formed. The abutting edges of the `notches 'are theny welded together and the bend or curved portion a, which is now finished, presentseverywhere a. cross section at least as great as that of the tube b itself (Fig. 4)

vand isalso amply strong'enough to withstand the steam pressure.

ain super-heater tubes madcas above described will remain exactly the same no matter how close together the two legs b, b

may be\brought. But in practice the distance between the legs should be sufficient to enable the welding ofthe notch edges toV bethoroughly and conveniently done and this will ordinarily be not less than about It is desirable also that there should be sutlicient room between the legs to permit the tire gases to have free circulation over the entirevsurface of each leg.

`1o5 The desirable characteristics of the bend Superheater tubes b comprising a return bend a formed and arranged in the manner described can be arrangcd inside the. smoke tubes l of a boiler the internal diameter or cross sectional arca of the smoke tubes being utilized to the best 'advantage while-at the same time there is no unnecessary restriction of the cross sectional area of the boiler tubes.

The ret-urn bend a for the superheater tubes Z) formed and arranged in accordance with 4the present invention therefore permits ofthe use of superheater tubes of the laigest possible cross section without-any restriction of area at the bend and` with the smallest possible'res'triction of the'cross section of the smoke tubes.

In l the embodiment illustrated in the l drawings I'have shown the notches c, c as V shaped and cut to about the middle oi the superheater tube z'. e., to a depth-equal to' about one-half the diameter of the tube and this typeand depth of notch I prefer; but

I findthat notches of' other types and depths will also enable me lto .produce superheater tubes capable of performing the purposes of my invention. l Furthermore while, in the' v embodiment referred to, I have s'hown'two notches foreach return bend, the numberoi' notches is not a necessary feature of my invention in its broader aspect.'

- While I have described my invention as embodied'in a smoke tube superheater I may, without- `departing from .the spirit of the invention, use it in otherforms of heating apparatus, in which a pair of legs united by a return bend as one element is inserted j in a tube as another element one of said elements carrying f a heatingv medium` and the other a medium to be heated.

Having described. my invention, I now `1.In a heating apparatus, two tubes in combination, one of said tubes being located within the other and comprising two legsv united by a return bend having an internal' cross-section at least as great as that of the Alegs, said bend lying substantially entirely .between the opposite 'outer portionscf the peripheries of the'two legs, one. of said tubes being adapted for the4 passage [of a heating medium and the other for the passage of a medium to be heated.

b 2. In a heating apparatus, twotubes in combination, one of Vsaid tubes being located within the.' other and comprising twolegs `listanced from one another by less `than their own diameter and united by a return bend having an internal crossisection at least as great as'that ofthe legs, said bend lying substantially entirely between the oppositeouter portionsfof the peripheries of the two legs, one of said tubes being'adapted y combination, one ofA said tubes being located within the other and :comprising two legs substantially Jg apart and united by a return bend having'an internal cross-section at least as great as that of the legs said bend lying substantially entirely between the opposite outer portions of the periphpp -fe'ries of the two legs, one of said tubes be-.ibfroin one anotherA by less than 'their own ing adapted. for the passage ot' a heating 65 medium. and the other for the passage of a medium to be heated.

4. In a heating apparatus, in combination, a straight tube and a.` tube located in said straight tube comprising two legs distanced from one another by less than their own diameter and integrally -united by a return bend having an internal cross-section at least as great as that ofthe legs,

said bend lying substantially entirely be- 75 tween the opposite outer portions of the peripheries ottlie two legs, one of said tubes being adapted for the passage of a heating medium 'and the other for the passage of a. medium to be heated.

5. In -a heating apparatus, two tubes in combination, one of said tubes being located within the other and having substantially uniform wall thickness throughout and further comprising two legs distanced from .8a

oneanother by less than their own diameter and united -by a return bend having an internal cross-section at least as great as that of thelegs, said bend lying substantially entirely between the o-pposite outer portions of the peripheries of the two legs, one of said-tubes being adapted for the passage of a heating medium and the other for the passage of a medium to be heated.

6. -In a superlieater of tlietype described,

in combination, assmoke. tube, and a super- .heater tube within said smoke tube comprising two legs'distanced from one anotherby less than their own diameter and united by a return bend having'an internal .100

cross-section at -least as .great as that of the legs said bend lying substantially entirely between the opposite outer portions of the peripheries of the two legs.

7. In a superheaterfof thetype described,

in combination, a.'smoke tube and a super- .heater tube within said smoke tube having' substantially uniform wall thickness and further/comprising two legs distanced from one\ another by'less thantlieir own diameter and '110'- llli' has been notched upon one side, bent about said I*notches "until the'notch edges `abut and then welded at theedges of said notch.

9. 'In a superheater of the type described, in combination, a smoke 'tube and asuperheater tubeof substantially uniforink wall thiclehess within said smoke tube said superheater vtube comprising two legs dist'aced jing, furthermore, substantially entirely be- Witnesses:

diameter and united by :t return bendhav-- In testimony whereof I have hereunto set ing an internal cross-secti0n at leash-.as my hand in the 'presence' of two subscribing l0A great as that of the legs and having a Weld Witnesses. A Y extending from the inner surface of Athe bend radially outward said returnbend ly- THEODOR MARTIN RENDCHEN" tween the opposite outer portions ofthe pe-' 'FRANZ KNEIFEL,

ripheries of the two legs. NQRAv VVILKEN. 

